Apparatus for scoring plastic tamper indicating closures and method for preparing the apparatus

Abstract: A method and apparatus for scoring plastic tamper indicating closures to provide the tamper indicating band that is connected to the closure by bridges formed by scoring. The scoring is achieved by successively moving a rotating closure past a stationary primary knife blade (33) having an arcuate concave interrupted cutting edge to form the bridges and then past a secondary knife (34) blade having an arcuate concave uninterrupted cutting edge to accurately dimension the bridges. The method and apparatus provides for supporting each knife blade (33,34) on a holder (40) wherein the position of the blade can be set by setting the blade (33,34) into a knife blade holder (40) using a setting fixture (60) remote from the apparatus, clamping the blade (33,34) within the knife blade holder (40), transferring the knife holder (40) to a machine mounting on the apparatus, then attaching the knife holder to the machine mounting without further adjustment, such that the arcuate knife blade is aligned with the center of the radius of the arc of each arcuate knife blade lies on a radial line from the curvature of the cutting edge to the center of the apparatus Each knife blade holder (40) is preferably mounted on a slide (41) on the rotary apparatus such that the arcuate edge can be adjusted so that the concave arc is parallel to the path of travel of the mandrels and at the required depth from the successive scoring.

Description: This invention relates to a method of preparing and to an apparatus for forming a circumferential score in a plastic closure according to the preambles of claims 1 and 6, respectively. Such scores are used to define a tamper indicating band on the closure connected to the peripheral skirt by a plurality of bridges. The bridges are broken when the closure is removed from a container. Background of the Invention CA-A-1,161,611 shows scoring of bottle caps by conveying the caps with a turret along an arcuate knife. The knife is clamped in a knife holder which can be adjusted by adjusting means formed by a threaded rod with a knob thereon. One type of tamper indicating closure includes molded circumferentially spaced bridges in order to define a tamper indicating band on the closure. Such construction requires costly more complex molds which also require maintenance. Typical patents showing such tamper indicating closures comprise US-A-4,613,052, 4,721,218, 4,801,031, 5,090,246 and 5,090,788. Another type of tamper indicating closure comprises utilizing an interrupted edged knife to produce bridges such as shown in US-A-4,322,009. In another type of tamper indicating closure, circumferentially spaced axial bridges are provided on the internal surface of the skirt of the closure and a continuous straight edged knife is applied from the exterior surface cutting through the wall of the closure and into the bridges. Such a construction also requires costly complex molds that require maintenance and necessitates relatively thin walls on the closures. A typical patent showing such a construction comprises US-A-4,545,496. In EP-A-0 621 475 A1 a tamper indicating closure is shown which comprises a base wall and a peripheral skirt having an internal thread adapted to engage the threads of a container wherein a tamper indicating band is provided on the skirt by a plurality of circumferentially spaced bridges. The band includes portions adapted to engage an annular bead on the container. The bridges are formed by using a primary knife having an interrupted cutting edge to produce a circumferential score in the side wall of the closure leaving spaced connectors or bridges. A secondary knife is used having a continuous uninterrupted cutting edge to provide a continuous external score line to provide an accurately dimensional radial thickness of the bridges. In a preferred method and apparatus, the closures engage the successive primary and secondary knives and are moved such that the closures roll relative to the knives. In such apparatus, each arcuate knife is mounted directly onto the apparatus, and its radial position and concentricity are set while the knife is mounted on the apparatus, using adjusting micrometer screws, one at each end of the arcuate blade. Such an apparatus has the disadvantage of loss of machine productive time while the operator is setting blades. It is also difficult to maintain knife concentricity with the center of rotation of the apparatus. This requires operator skill in setting of the knives, and effective maintenance of the arcuate setting. Summary of the Invention The invention is based on the problem of setting knifes or blades without loss of machine production time. This problem is solved by the method of claim 1 and the apparatus of claim 6. Among the objectives of the present invention are to provide an apparatus utilizing successive arcuate cutting knives wherein each knife blade is accurately set utilizing a remote setting fixture and the method of preparing it; wherein the setting fixture does not require the use of a dial indicator and, therefore, is not affected by the variability of the dial indicator setting and needs less skill in use; wherein the setting fixture cannot be over adjusted; and wherein the adjustment is less dependent on operator skill. In accordance with the invention, a method and apparatus for scoring plastic tamper indicating closures to provide the tamper indicating band that is connected to the closure by bridges formed by scoring. The scoring is achieved by successively moving a rotating closure on rotating mandrel past a stationary primary knife blade having an arcuate concave interrupted cutting edge to form the bridges and then past a secondary knife blade having an arcuate concave uninterrupted cutting edge to accurately dimension the bridges. The method and apparatus provides for supporting each knife blade on a holder wherein the position of the blade can be set by setting the blade into a knife blade holder using a setting fixture remote from the apparatus, clamping the blade within the knife blade holder, transferring the holder to a machine mounting on the apparatus, then attaching the holder to the machine mounting without further adjustment, such that the arcuate knife blade is aligned such that the center of the radius of the arc of each arcuate knife blade is substantially coincident with the center of the apparatus. Each knife blade holder is preferably mounted on a slide on the rotary apparatus such that the arcuate edge can be finely adjusted so that the concave arc is parallel to the path of travel of the mandrels and at the required depth for the successive scoring. The method and apparatus includes: 1. Remote setting of an arcuate knife blade using an adjustment knob with a built in torque limiter, to drive a cam which in turn moves a blade to a predetermined position against a fixed stop, with a controlled force. 2. The provision of a machine slide having a mounting suitable for the knife blade such that the linear movement of the slide is radial to the center of rotation of a turret apparatus, clamping of an arcuate knife blade with a holder while the knife blade is securely held in a preset position, such that when transferred to the machine mounting, the arcuate knife blade will be aligned such that both the center of the radius of the arc of the arcuate knife blade and the midpoint of the arc lie on a radial line from the center of the turret apparatus parallel to the linear adjustment of said slide. 3. Linear adjustment means by a micrometer screw on the machine, and position indication by digital indicator to enable minor changes in the depth of radial cut of the blade on the machine. Description of the Drawings FIG. 1 is a fragmentary plan view of a rotary scoring apparatus embodying the invention. FIG. 2 is a sectional view taken along the line 2-2 in FIG. 1, parts being broken away. FIG. 3 is a fragmentary partly diagrammatic plan view of a portion of the apparatus shown in FIG. 1. FIG. 4 is a fragmentary part sectional elevational view of a portion of the apparatus taken along the line 4-4 in FIG. 3. FIG. 5 is a fragmentary elevational view taken along the line 5-5 in FIG. 3. FIG. 6 is a fragmentary sectional view taken along the line 6-6 in FIG. 3. FIG. 7 is a partly diagrammatic plan view showing one of the knife blades having an interrupted cutting edge mounted on the apparatus. FIG. 8 is a plan view of a setting fixture with the knife blade shown in FIG. 7 mounted thereon. FIG. 9 is a sectional view taken along the line 9-9 in FIG. 8. FIG. 10 is a partly diagrammatic view of the apparatus cams utilized in the rotary apparatus for moving the closures into each of the knife blades and raising and lowering the tooling as the apparatus rotates. FIG. 11 is a fragmentary elevational view of a portion of the cams on the apparatus. FIG. 12 is a fragmentary plan view of a portion of the apparatus. Referring to FIGS. 1, 2 and 4, the method and apparatus embodying the invention includes a rotary scoring machine or apparatus 20 that has a base 21. A column 22 is mounted on the base 21 and a turret 23 is mounted for rotation on the column 22 by spaced bearings 24, 25. The turret 23 supports a plurality of sets of tooling including an upper tooling 26 and a lower tooling 27. The upper tooling 26 functions to hold a closure C in position on the lower tooling 27 so that it can be moved and rotated past successive arcuate knife blades, as presently described. Closures C are made of plastic, such as polypropylene, by injection molding or compression molding and comprise a base wall and peripheral skirt. The tamper indicating function is provided by a score line and is preferably of the type shown in US-A-5,090,788. Closures C are moved successively into the turret 23 and onto support pads of the lower tooling by a starwheel 30. Af ter the closures C are scored, they are removed from the turret by a starwheel 31 (FIG. 1). Referring to FIG. 3, each closure C includes a base wall and a peripheral skirt and is moved past successive cutting knife blades 33, 34 mounted on holders, as presently described. The knife blade 33 has an interrupted concave arcuate cutting edge and the knife blade 34 has a continuous concave arcuate cutting edge such that as a closure C is moved by the turret and the closure is rotated into the successive knife blades, the primary knife blade 33 produces a circumferential score in the sidewall of the closure leaving spaced connectors or bridges and the secondary knife blade 34 provides a continuous external score line and an accurately dimensional radial thickness of the bridges, as more fully discussed in EP-A-0 621 475 A1. Each knife blade 33, 34 is in the form of a flat blade clamped in a knife blade holder 40 which is mounted on a linear machine slide 41 which is in turn mounted on the machine base 21 such that the linear slide 41 is radial to the rotation of a machine mounted turret (FIG. 6) . Referring to FIG. 2, each set of upper tooling 26 on the turret 23 includes a mandrel 43 with its axis parallel to the axis of rotation of the turret 26. Each mandrel 43 is rotated past an arcuate fixed gear 44 as the turret is rotated and a pinion gear 45 on each mandrel 43 meshes with fixed gear 44 to rotate the mandrel. A closure C is carried on each mandrel 43 and is brought successively into tangential contact with the blades 33, 34 such that scoring takes place in the side wall or skirt of the closure C to delineate the band. The rotation of each closure C preferably is a substantially true rolling motion with each blade. Each arcuate blade 33, 34 is designed such that at the desired depth of cut, the blade cutting edge is concentric to the turret center of rotation. A blade setting fixture 60 enables the pre-setting of each arcuate blade 33, 34 in the holder 40 such that when transferred to the machine mounting the arcuate blade will be aligned such that both the center of the radius of the arc of the arcuate blade and the midpoint of said arc lies on a radial line from the center of the turret parallel to the linear adjustment of the machine slide on which it is mounted. Thus, by linear adjustment of the machine slide, a position can be established whereby the blade arc is concentric to the center of rotation of the turret. Each knife blade holder 40 includes knife blade holding plates 46a, 46b between which a knife blade 33 or 34 is clamped by headed screws 47. The knife blade has openings through which screws 47 extend. The plates 46a, 46b and knife blade holder further include openings 48, 49, 50 for engaging dowels 51 on the dovetail slide 52 on the base 21 of the apparatus (FIGS. 3, 4). Each knife blade 33, 34 is adjusted in a fixture 60 in a similar manner. When in position on the machine, the radial depth of scoring of each knife blade can be controlled by rotating a knob 54 on the slide in visual guidance by a visual dial indicator 59. This construction comprises a screw 55 on which knob 54 is mounted. Screw 55 is journalled on slide 52 and engages a nut 56 fixed on base 53. Referring to FIGS. 8-10, the blade setting fixture 60 includes a base 61, a pair of pilot holes 62 for the mounting of fixed cylindrical stops 63 in the form of rolls and a pair of cam shafts 64 supporting eccentric cams 65 connected to the shafts 64 by torque limiter knobs 66. The fixture includes a diamond shaped dowel 57 and a regular dowel 58 (to allow for pitch error) and securing screws (not shown) so as to replicate the machine mounting of the knife holder 40 on the base 61. The fixed stops 63 are machined to preset dimensions for each particular blade profile/cap diameter combination, and selected and fitted accordingly. For setting, a blade is secured snugly but free to move within the holding plates 46a, 46b and the assembly is mounted onto the setting fixture 60. By carefully rotating the adjustment knobs 66, the blade is moved toward the fixed stops 63 until the blade cutting edge contacts the stops 63. By continuing the adjustment until the torque limiter knobs 66 slip, the final blade position is reached and the blade can be finally clamped between the holder plates 46a, 46b, by tightening screw 47. The blade arc will change for differing closure diameters, and within a limited range it is possible by geometry to ensure that the fixed stops 63 are designed such that a particular "zero" position of the slide as indicated by the digital indicator on the slide, would be the correct position for the desired depth of cut. For closure diameters outside this range, it may be necessary to establish a different slide position f or which the desired depth of cut would be theoretically correct in order that the blade projection from the blade holder is held to a practical minimum. However, due to variability in the parts, and the need to exactly control the depth of cut to ensure adequate band performance, it may be necessary to marginally deviate from this desired setting. The slide 52 provides this adjustment and as mentioned is equipped with a digital indicator 59 to provide accurate feedback on the radial adjustment. The resulting minimal blade arc eccentricity to the turret center of rotation is negligible in practice. Cams 70, 71 are provided for lifting and lowering the closure C on the lower tooling 27 into engagement with mandrel 43 by engaging rollers 72, 73, respectively, on an actuator 75 which supports a closure supporting pad 84. A cam roller 77 extends into a slot 78 on the turret 23 to guide the vertical movement of pad 84 (FIGS. 2, 10-12). Referring to FIG. 2, in accordance with another aspect of the invention, each set of lower tooling 27 comprises a block 80 fixed on a shaft 81 slidable in upper and lower linear ball bearings 82, 83 and with antirotation means comprising the roller 77 on the block 80 operating in slot 78 on the turret 23. Block 80 supports spring loaded closure support pad 84. In this manner, there is provided a large length to diameter ratio in bearings 82, 83 thereby providing improved lateral support to the closure support pad 84 and maintaining a compact configuration in the vertical axis. In addition, the tooling 27 is more readily accessible for changing the tooling. It can thus be seen that there has been provided a method and apparatus utilizing successive arcuate cutting knives wherein each knife blade is accurately set utilizing a remote setting fixture; wherein the setting fixture does not require the use of a dial indicator and, therefore, is not affected by the variability of the dial indicator setting and needs less skill in use; wherein the setting fixture cannot be over adjusted; and wherein the adjustment is less dependent on operator skill.

Claims: A method of preparing an apparatus for forming a circumferential score in a plastic tamper indicating closure (C) having a base wall and a peripheral skirt, the apparatus comprising a rotary apparatus part (23) for moving the closures (C) on an arc about the center of rotation of this apparatus part past a scoring knife, and a stationary apparatus part (21) which includes: a knife (33, 34) having at least an arcuate concave cutting edge designed for being concentric to the center of rotation of the rotary apparatus part, and a knife holder (40) having clamping means (46a, 46b) for loosening and clamping the knife to hold the knife stationary during scoring of the closure (C), and the method being characterized by the steps of: providing first locating means (50) on the knife holder (40), providing second locating means (51) on said stationary apparatus part which are engageable with the first locating means (50), providing a fixture (60) having third locating means (57, 58) for locating the knife holder (40) on said fixture (60) by engagement with said first locating means (50) and having spaced stops (63) defining an arc of engagement with the arcuate cutting edge of the knife such that the arc of the knife blade is at a predetermined position relative to the holder (40) when the edge engages said stops, positioning said knife (33,34) in the knife holder (40) positioning said knife holder (40) on said tixture (60), moving said knife (33, 34) relative to the knife holder (40) against said stop means (63) with a predetermined force, tightening said clamping means (46a, 46b) to clamp said knife (33, 34) relative to said knife holder (40), removing the knife holder (40) from said fixture (60), positioning said knife holder (40) on said stationary apparatus part (21) by engaging said first locating means (50) of the knife holder (40) with said second locating means (51) on said stationary apparatus part (21) such that the arcuate edge of said knife is arcuately positioned and the center of the radius of the arc of the knife substantially corresponds with the center of rotation of the rotary apparatus part (23) and lies on a radial line of the rotary apparatus part. The method set forth in claim 1 wherein said step of providing locating means for said knife holder (40) comprises providing complementary dowels (51; 57, 58) and openings (50). The method set forth in claim 1 wherein said step of moving said knife (33, 34) against stop means (63) comprises engaging the edge opposite to the cutting edge of the knife and providing a predetermined force on said opposite edge of the knife. The method set forth in claim 1 including providing a mandrel (43) on said rotary apparatus part (23) for holding said closure (C) and providing a support associated with said mandrel (43). The method set forth in any one of claims 1-4 wherein said steps of positioning and moving said arcuate knife (33, 34) are such that the center of the midpoint of the arc lies on the radial line and including providing a slide (41) on said stationary apparatus part (21) on which said knife holder (40) is positioned and moving the knife holder (40) on said slide (41) to finely adjust the knife such that the concave arc is parallel to the path of travel of the closures (C) and at the required depth for scoring. An apparatus for forming a tamper indication closure from a plastic closure (C) having a base wall and a peripheral skirt, by forming a circumferential score comprising: a rotary apparatus part (23) for moving the closures (C) on an arc about the center of rotation, of this apparatus part past a scoring knife, and a stationary apparatus part (21) which includes: a knife (33, 34) having at least an arcuate concave cutting edge designed for being concentric to the center of rotation, and a knife holder (40) having clamping means (46a, 46b) for loosening and clamping the knife to hold the knife stationary during scoring of the closure (C), characterized in that the knife holder (40) has first locating means (50) engageable with second locating means (51) of said stationary apparatus part (21) so that the knife holder (40) together with the knife (33, 34) can be removed from, and refitted onto the stationary apparatus part (21), a remote fixture (60) having third locating means (57, 58), is provided for receiving said knife holder (40) together with the knife (33, 34) when removed from the stationary apparatus part (21), the fixture (60) has stop means (63) defining an arc for engagement with the arcuate cutting edge of the knife (33, 34), and shifting means (64, 65, 66) for moving the knife (33, 34) relative to the knife holder (40) and against the stop means (63) with a predetermined force, said stop means comprises spaced stops such that when the arcuate edge of said knife blade engages said stops, it is positioned such that the arc of the knife blade is at the predetermined position relative to the holder, the clamping means (46a, 46b) of the knife holder (40) are adapted to be tightened to fix the position of the knife relative to the knife holder as adjusted by the fixture (60), and the knife holder (40), together with the knife (33, 34) fixed therein, by virtue of its first locating means (50) fits to said second locating means (51) of the stationary apparatus part (21) with the center of the radius of the arc of the knife substantially corresponding with the center of rotation of the rotary apparatus part (23). The apparatus set forth in claim 6 wherein said first, second and third locting means comprise dowels (51, 57, 58) and openings (50) which are complementarily shaped and mate with one another. The apparatus set forth in claim 6 or 7 wherein said means for moving said knife (33, 34) against stop means (63) comprises rotatable spaced eccentric cams (65) which can be rotating to move the knife against said stop means (63). The apparatus set forth in claim 8 including force limiting means (66) associated with said rotatable cams (65). The apparatus set forth in any of claims 6 through 9 wherein said rotary apparatus part (23) comprises a plurality of mandrels (43) for holding said closures (C), a plurality of support pads (84) on which closures (C) are supported, each support pad (84) being provided on a block (80), a shaft (81) on which said block (80) is mounted, and spaced linear bearings (82, 83) for supporting said shaft (81) for vertical linear movement. The apparatus sets forth in any one of claims 6 through 10 wherein said stationary apparatus part (21) includes successive slides (41), each supporting a successive knife holder (40) with a successive blade (33, 34) to form said knife having said at least arcuate concave cutting edge.

Inventors: INGRAM KEITH W, INGRAM, KEITH W.
Applicants: OWENS ILLINOIS CLOSURE INC, OWENS-ILLINOIS CLOSURE INC.
Application year: 1994
Main classification: B26D7
IPC codes: B29L31, B26D7, B65D41, B29C69, B29D99